A correct diet lies at the base of wellbeing and good health. In order to eat healthily, we must take in all nutrients in a balanced manner, choising the ones that increase benefits to our organism.
Extra virgin olive oil, is a concentrated source of energy, an irreplaceable carrier of essential fatty acids and the ideal vehicle for natural fat-soluble vitamins. the use of olive oil in nutrition is a beneficial factor for the function of the digestive system due to its property of keeping low the percentage of HCl in our stomach. Thus, the olive oil helps the normal function of the digestive system reducing to minimum the chances of ulcer creation and the other relative diseases, as gastritis. In fact  Olive oil activates the secretion of bile and pancreatic hormones and It produces the best results  for the regulation of the pyloric antrum ,improving the cholagogic and choleretic functions of the gall bladder – . Consequently, it lowers the incidence of gallstone formation.  
The use of olive oil also produce good results for the intestinal motility.
Cardiovascular diseases are caused by the hardening and stiffening of arteries due to the formation of atheromatous plaque leading to the progressive narrowing of the blood vessels. The consumption of olive oil increases low-density lipoproteins (LDL) which favour the formation of “bad cholesterol” deposits and prevent the lowering of high-density lipoproteins (HDL). Omega 3 fatty acids in olive oil nourish cardio vascular system and clear the plague in arteries, so arterial walls become more elastic and strong , and the result is a major reduction in the rate of cardiovascular disease and arteriosclerosis. But olive oil-rich diets not only reduce LDL cholesterol levels, but also lower blood sugar levels and decrease insulin requirements in persons with type 2 diabetes.
Olive oil greatly influences the development of fetus during pregnancies and  the main component of olive oil also plays a fundamental role in the development of the nervous system of newborn babies, as the formation of the myelinic membrane requires saturated, polyunsaturated and monounsaturated fatty acids in the diet. In this context, it is worth mentioning that breast milk is very rich in oleic acid.
it has also been proved that the use of olive oil in nutrition helps to sustain the metabolism at a good balance, the body's growth and bone growth at a good level. It is obvious that olive oil means good health and development for children.
The ageing of cells in the human body occurs as a result of an oxidation process, leading to the formation of free radicals. These are highly aggressive molecules having a negative influence on the viability of the cells themselves. The performance of antioxidants in olive oil helps to retard cellular growth and, as a result, contributes to making the ageing process in the human body both slower and healthier.
Recent studies revealed that olive oil, thanks to the “oleocanthal” a natural compound contained in it, play a key role to inhibits activity of COX (cyclooxygenas) enzymes, underliesing its anti-inflammatory  actions. (Monell Chemical Senses Center – Philadelphia, U.S.A. – research directed by biologist Gary Beauchamp, PhD, and by sensory scientist Paul Breslin, PhD) .The conservation of cell structure from the deterioration caused by oxidation is closely linked to lower rates of tumours. The consumption of olive oil, especially the positive action of oleic acid, acts to prevent or weaken the appearance of cancer, as less oxidative damage occurs. It is clear that with many types of cancer – brest, lung, oral cavity, pharynx, esophagus, colon, ovary and prostate - there is a significantly lower rate of occurrence when the main dietary fat is olive oil.
A study from Northwestern University in Chicago has been shown that  oleic acid reduce the expression of the Her-2/neu oncogene, which is associated with the aggressive growth of breast cancer tumors. High levels of Her-2/neu are found in one-fifth of breast cancers, especially those that are resistant to treatment. Professor Menendez and his colleagues from Northwestern University exposed two strains of aggressive breast cancer cells to oleic acid, levels of Her-2/neu dropped 46%. When they combined oleic acid with lower levels than are normally used of Herceptin - a drug used to treat breast cancer - oleic acid greatly enhanced the effectiveness of the drug, dropping Her-2/neu expression as much as 70%. The end result: oleic acid promoted the apoptotic cell death (suicide) of aggressive, treatment resistant, breast cancer cells.
Therefore we can say that olive oil is the best nutritional gift we can offer to ourselves. Olive oil helps us keep good in health making our life pleasant.

Fonts:

• Biblioteca Europea Medica Informativa sull’Olio d’Oliva
• CORDIS Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo
• Dossier Informativi CEE/DG VI
• INRAN Istituto Nazionale di Ricerca per gli Alimenti e la Nutrizione
• LILT Lega Italiana per la Lotta contro i Tumori
• Linee Guida per una Sana Alimentazione Italiana - Edizione 2003
• Ministero della Salute
• Ministero delle Politiche Agricole, Alimentari e Forestali
• OMS Organizzazione Mondiale della Sanità